Geosmin and 2-methylisoborneol are volatile organic compounds frequently found as contaminants in drinking water and fish raised by aquaculture methods. Although not toxic to humans, geosmin and 2-methylisoborneol are generally associated with an undesirable musty or muddy taste and odor in the sources in which they are present. Geosmin and 2-methylisoborneol are generated by a variety of microorganisms, including several species of cyanobacteria, as products of pathways that include geosmin synthase and 2-methylisoborneol synthase. Currently, geosmin and 2-methylisoborneol are detected after their production by an unpleasant odor in a source. Early detection of sources of microbial contamination, for example, prior to an unpleasant odor, may be important in developing effective remediation plans for reducing or eliminating geosmin and 2-methylisoborneol contamination in natural resources, including water, food sources and other materials. Thus, there is a need to develop new, improved and effective methods for detecting microbial sources of geosmin and 2-methylisoborneol contamination.